Approximately 1 million people are engaged in firefighting. More than 250 of these lost their lives and about 100,000 were injured between 1990 and 1992. This activity is even more dangerous due to exposure to hazardous materials (hazmat). However, little information is available on the adverse health effects of the high levels of toxic chemicals generated and the likelihood of their being present in mixtures to which the firefighters are exposed. The proposed research will continue the prospective study of an established cohort of hazmat firefighters and a second group consisting of regular duty firefighters. Baseline and periodic questionnaire data as well as physical and laboratory data have been obtained and will be reviewed yearly during the study. An existing database on incidents to which the 6 Massachusetts district hazmat teams have responded since their beginning is updated periodically. The specific aims of the proposal include: 1) Prospective evaluation of possible clinical and subclinical health effects from fighting fires containing hazardous materials; 2) Analysis of the clinical utility and cost effectiveness of current medical surveillance tests; 3) A longitudinal study of pulmonary function in firefighters and the potential relation to the acute respiratory effects of firefighting; 4) Systematic investigation of hazmat accidents and the associated injuries to facilitate developing improved training, safer firefighting practices and means to prevent future incidents and 5) Characterization of the number and types of incidents that hazmat teams respond to and determine the number of responders that sustained injury or required acute treatment. Since firefighters are involved in unpredictable and dangerous work environments which do not fit traditional industrial hygiene controls, improved medical surveillance and knowledge of long-term health sequelae and preventive measures are needed.